Pump for use in a vacuum cleaner

ABSTRACT

A pump is for generating a suction for application to a vacuum cleaner dirty air inlet. There is a motor inside a motor outer casing and a fan outside the motor outer casing having a main inlet and a main outlet. The fan generates a main suction flow between the main inlet and the main outlet and creates a region of under pressure. This under pressure is used to drive a secondary flow between a cooling air inlet to the motor outer casing and a cooling air outlet from the motor outer casing. The secondary air flow is induced by making use of an under pressure generated by the fan.

FIELD OF THE INVENTION

This invention relates to a vacuum cleaner pump, and in particularrelates to a pump suitable for use as part of a wet (or wet and dry)vacuum cleaner.

BACKGROUND OF THE INVENTION

For wet vacuum cleaners (or wet cleaning devices more generally) thereis always a risk that an air flow still containing an amount of water orother dirt will reach the main fan motor, even though the air flow hasalready passed through a filter for separating the dirt and moisturecontent, such as a labyrinth filter or a cyclone.

In conventional dry vacuum cleaners, this main flow is used to cool themotor part, but this is not possible if the main air flow contains wateror other dirt. Water and other dirt in the motor part gives rise to ahigh risk of failure of the motor part.

A common solution for this problem is to use a so-called bypass motor.In a bypass motor there are two separate air flows. The main air flowtransports the dust, water and other dirt to the dirt management system,but it is guided and sealed in such a way that it is impossible for thismain air flow to reach the motor part.

A secondary air flow is created to cool the motor part. Normally thissecondary air flow is induced by adding a cooling fan to the motor part.A special set of channels is added in the appliance to guide this airflow from the outside of the appliance to, and through, the motor partand back again back to the outside of the appliance.

FIG. 1 shows a typical configuration of a pump with a bypass motor andfan. The pump 10 comprises a motor 12 with a spindle a fan 14, adiffuser 15 and a fan casing 40. A main air flow enters the fan as anentrance flow 16 and exits as an exit flow 18 from a main outlet 19. Thesecondary flow comprises an inlet flow 20 and an outlet flow 21 which isgenerated between a cooling air inlet 22 and a cooling air outlet 24.

The motor 12 includes an additional cooling fan to generate thesecondary flow. The cooling fan is typically an axial flow fan, which isnot normally very efficient because it is designed for flow generationrather than pressure generation. As a result, the channels to bring theflow to the motor part have to be rather large in diameter.

The additional cooling fan also takes up space, typically along theaxial direction of the motor. This increase in axial length decreasesthe resonance frequency of the shaft which means a thicker shaft isrequired.

In the case of a brush motor, the outlet flow 21 may contain carbonbrush particles. This can also have a negative impact on the dustemission of the complete appliance, or else an extra set of filters mayhave to be added in the bypass circuit.

There is therefore a need for an improved pump design to implement asecondary cooling flow. A vacuum cleaner with a means for cooling themotor is known from for instance EP0650690A1.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention,there is provided a pump for use in a vacuum cleaner for generating asuction for application to a vacuum cleaner dirty air inlet, comprising:

a motor outer casing;

a motor part in the motor outer casing;

a fan outside the motor outer casing, driven by the motor part, having amain inlet and a main outlet, wherein the fan generates a main suctionflow between the main inlet and the main outlet and creates a region ofunder pressure;

a cooling air inlet to the motor outer casing;

a cooling air outlet from the motor outer casing; and

a fluid coupling between the cooling air outlet and the region of underpressure such that a secondary flow of air is sucked through the coolingair inlet resulting in a cooling of the motor, wherein the cooling airinlet (22) and the main suction flow (16,18) are separated from eachother.

This pump has a motor which drives a fan to generate a main suctionflow. The main suction flow for example carries dust and air, andoptionally also water for a wet vacuum cleaner, through a dirtmanagement system. The dirt management system is typically upstream of(i.e. before) the pump. A separate secondary air flow provides motorcooling, so that the main suction flow is not used for cooling. Thesecondary air flow is induced by making use of an under pressuregenerated by the fan.

Thus, the secondary air flow does not need a separate fan. Instead, anunder pressure generated by the fan is used to draw into and out of themotor outer casing. Air may be drawn in from the cooling air inlet (anddisplacement causes air to be expelled from the cooling air outlet) orit may be drawn out from the cooling air outlet (and displacement causesair to be drawn in from the cooling air inlet). The air delivered to thecooling air inlet is for example from the ambient surroundings.

The dirty air inlet may be a nozzle, tube, cleaning head or any othervacuum accessory.

The secondary flow results in a bypass motor design. The inventionenables a standard dry pump assembly to be used with only minoradaptation. In particular, only the main flow fan is used.

The cooling air inlet and the main suction flow are separated from eachother in the sense that there is no path in use from the main suctionflow to the cooling air inlet. This may rely both on the physicalpassageways but also the pressure differentials that arise in use. Themain suction flow is thus not used for cooling of the motor and it isprevented that the main suction flow enters the cooling air inlet andthereby forms the secondary flow.

The fan is preferably located inside a fan casing. The fan casing may beused to provide pressure differentials between different areas, and thusmay have a role in defining the pressure levels to promote the secondaryflow.

The region of under pressure created by the fan is preferably located atleast partially inside the fan casing and outside the motor outercasing.

In a first example, the region of under pressure created by the fancouples to an inlet side of the fan.

In this case, the region of under pressure is fully outside the motorouter casing. The secondary flow then defines a passageway between aninner volume of the motor outer casing and the inside of the fan casingat the inlet side of the fan. Once the secondary flow reaches the inletside of the fan, it combines with the main flow.

In a second example, the region of under pressure created by the fan islocated adjacent the motor outer casing and couples to the inside of themotor outer casing.

In this case, the fan generates an under pressure which couples to theinside of the motor outer casing, but with separation provided betweenthat area of under pressure and the main suction flow.

For this purpose, the fan may have a front side outside the motor outercasing and a back side which faces and couples to the inside of themotor outer casing, wherein the front side generates the main suctionflow and the back side acts as a pump to generate said region of underpressure.

Thus, the fan is used to generate the region of under pressure for thesecondary flow using a back of the fan. The fan has front and backfunctional parts. The back part of the fan functions as compressor togenerate a pressure differential and this couples to the inside of themotor casing. The boundary between the front and back sides of the fanprovides separation between the main suction flow (on the front part ofthe fan) and the secondary flow (on the back part of the fan).

However, the main flow and the secondary flow may combine downstream ofthe motor outer casing to create a combined air outlet.

The fluid coupling for example couples to a region of maximum underpressure at the front side of the fan or at the back side of the fan.This enables a greatest possible secondary flow to be generated.

The main inlet may be an axial inlet in front of the fan and the mainoutlet may be a radial outlet. The use of a radial fan in this waygenerates a large under pressure, and is therefore particularly suitablefor generating the desired secondary flow. However, other fan types maybe used such as a mixed flow or an axial fan.

The main outlet of a radial fan is for example directed around theoutside of the motor outer casing. The flow may thus also provide acooling function around the outside of the motor outer casing.

The cooling air inlet is for example coupled to the ambientsurroundings. Thus, ambient air is used for the secondary flow.

The motor is for example a brushless dc motor or a permanent magnet dcmotor.

The invention also provides a pump and filter unit, comprising:

the pump as defined above; and

a filter section downstream of the pump.

By having a filter section downstream of the pump, the secondary airflow, namely the cooling air flow, may also be subjected to filteringbefore it is expelled back to the ambient surroundings, in the same wayas the main air flow. If using a brushed motor, the cooled air caninclude entrained carbon particles. Thus, a post motor filter will alsofilter these carbon particles.

The invention also provides a vacuum cleaner, comprising:

a main body including the pump as defined above;

a vacuum cleaner dirty air inlet coupled to the main body for receivinga suction generated by the pump; and

a dirt separation unit upstream of the pump.

The use of a bypass motor (with a separate secondary cooling air flow)is particularly desirable for a flow which contains water, since thewater content is prevented from being used a part of the coolingprocess. The design is thus suitable for a wet vacuum cleaner.

There is for example also a filter section through which the flowgenerated by the pump is passed, the filter section being downstream ofthe pump. This downstream filter processes both the main suction flowand the secondary flow, downstream of the pump.

The vacuum cleaner may further comprise control electronics, wherein thecontrol electronics is cooled by the secondary flow of air. Thus, inthis way, the cooling circuit not only cools the motor but also coolsthe electronics.

The vacuum cleaner may further comprise control electronics, wherein thecontrol electronics is cooled by the secondary flow of air, after thesecondary flow of air has cooled the motor.

The vacuum cleaner may further comprise control electronics, wherein thecontrol electronics is cooled by the secondary flow of air, before thesecondary flow of air enters the motor outer casing. Thus, the controlelectronics can also be cooled by a dry air stream.

The invention also provides a method of cooling a motor of a vacuumcleaner pump which is for driving a fan to generate a main suction flowand a region of under pressure, the main suction flow being forapplication to a vacuum cleaner dirty air inlet, and the motor beingcontained within a motor outer casing, the method comprising:

providing a fluid coupling between a cooling air outlet of the motorouter casing and the region of under pressure, such that a secondaryflow of air is sucked through the cooling air inlet resulting in acooling of the motor.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearlyhow it may be carried into effect, reference will now be made, by way ofexample only, to the accompanying drawings, in which:

FIG. 1 shows a typical configuration of a pump with a bypass motor andfan;

FIG. 2 shows in schematic form an arrangement in accordance with theinvention;

FIG. 3 shows a perspective view of one example embodiment of the pump;

FIG. 4 shows a cross section through the pump of FIG. 3 .

FIG. 5 shows another cross section for the same design as FIG. 4 ;

FIG. 6 shows a cross section through a second example embodiment of thepump.

FIG. 7 shows one example of a vacuum cleaner to which the pump has beenapplied.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It shall be understood that the detailed description and specificexamples, while indicating exemplary embodiments of the apparatus,systems and methods, are intended for purposes of illustration only andare not intended to limit the scope of the invention. These and otherfeatures, aspects, and advantages of the apparatus, systems and methodsof the present invention will become better understood from thefollowing description, appended claims, and accompanying drawings. Itshould be understood that the Figures are merely schematic and are notdrawn to scale. It should also be understood that the same referencenumerals are used throughout the Figures to indicate the same or similarparts.

The invention provides a pump for generating a suction for applicationto a vacuum cleaner dirty air inlet, for example for connection to asuction head, nozzle, brush or any other suitable accessory. There is amotor inside a motor outer casing and a fan outside the motor outercasing having a main inlet and a main outlet. The fan generates a mainsuction flow between the main inlet and the main outlet and creates aregion of under pressure. This under pressure is used to drive asecondary flow between a cooling air inlet to the motor outer casing anda cooling air outlet from the motor outer casing. The secondary air flowis induced by making use of an under pressure generated by the fan.

The invention thus makes use of the main fan for creating a secondarycooling air flow. The main fan can be designed to be very efficient. Asa result, the cooling for the motor part is achieved with lower losses.

The main fan is for example a radial fan, providing high pressurecompared to an axial fan as normally used for cooling fans. The coolingcircuit can therefore tolerate higher pressure drops, and can thereforeuse fluid connections which are smaller in diameter.

Since no fan is added to the motor part for the secondary air flow, thepump, can be optimal in size with no need for additional space toaccommodate a cooling fan.

FIG. 2 shows in schematic form an arrangement in accordance with oneexample of the invention. FIG. 2 shows a cross section through the pumpof FIG. 1 with a modification of the invention explained in generalterms.

The entrance flow 16 is received at a main inlet 17 and the exit flow isdelivered from a main outlet 19.

The motor comprises a motor outer casing 30 and an internal motor part32 inside the motor outer casing 30. The fan 14 comprises a fan casing40 as mentioned above and a fan unit 42 (i.e. a fan blade arrangement).The motor drives an output shaft 34 at one end of which is mounted thefan unit 42. Between the fan and the motor casing 30 is a diffuser 15. Amotor spindle passes through the diffuser 15 to couple with the fan. Thediffuser comprises a set of blades for controlling flow characteristicsto create desired flow and pressure conditions.

A diffuser is a standard part of a vacuum pump design, for controllingthe flow characteristics of the fan 40. Different designs are possiblefor the diffuser.

The fan unit 42 generates an under pressure which is used to drawcooling air into the motor outer casing 30.

Arrow 44 shows that, in accordance with one example, an under pressureat the fan inlet can be coupled to the cooling air outlet 24 so that airis sucked from the outlet 24 and this is replenished by air drawn infrom the cooling air inlet 22.

An alternative (not shown) is that an under pressure generated by thefan is used to draw air in from the cooling air inlet 22 into the insideof motor casing 30 as the inlet flow 20.

The expelled outlet flow 48 rejoins the main suction flow.

FIG. 2 thus shows in schematic form the concept of the invention asapplied to conventional pump single fan pump, in particular by couplinga cooling flow outlet to a low pressure region of the fan.

The operation of the fan results in a region 49 a of under pressure.Inside the fan casing 40 of a centrifugal radial fan, the pressure isalways lowest at the center and it gradually increases and changes to anover pressure towards the outside of the casing. Thus, there is aradially outer region 49 b of over pressure. The kinetic energy of thefan blades create a centrifugal force acting on the air and thusaccelerate the air towards the radial outside of the casing. Air entersthe fan casing in an axial direction and leaves in a radial direction.

There is a fluid coupling between the cooling air outlet 24 and theregion of under pressure (in this example at the fan inlet side) suchthat the secondary flow of air is sucked through the cooling air inlet22 resulting in a cooling of the internal motor part 32.

By combining the cooling air with the main suction flow, the cooling airflow is cleaned of carbon particles (in the case of a brush based motor)by the same filter set (downstream of the pump) as is used to clean themain suction air flow. This allows low emissions without the need to addadditional filters for the cooling air flow.

FIG. 3 shows a perspective view of one implementation of the pump.

FIG. 3 shows that cooling outlet flow 21 and main exit flow 18 combineand mix to form the overall air flow path which proceeds downstream.

An isolating ring 50 is provided around the pump for isolating the inletflow 20 from the outlet flow 21 and main exit flow 18. The isolatingring 50 together with an overall casing can prevent interaction betweenthe outlet flow 21, main exit flow 18 and the inlet 22 or inlet flow 20.The outlet flow 21 and main exit flow 18 are for example routed to anoutlet tube while the back of the pump, at which the cooling air inlet22 is formed, is isolated from the main flow 16, 18. The cooling airinlet couples to the ambient surroundings.

FIG. 4 shows a cross section through one implementation of the pump ofFIG. 3 . This is for an example in which an under pressure generated bythe fan is used to draw air in from the cooling air inlet 22 into theinside of motor casing 30 as the inlet flow 20.

The fan unit 42 has a front side 42 a outside the motor outer casing 30and facing outwardly, and a back side 42 b facing inwardly. The backside 42 b couples fluidly to the inside of the motor outer casing 30.The front side 42 a generates the main suction flow, and in the exampleshown is a radial fan. Between the fan unit 42 and the motor outercasing 30 is the diffuser 15.

The back of the fan is separate from the front of the fan because it hasa structure of a solid plate which carries the fan blades. Thus, thepassage of moisture from front to back is prevented.

The back side 42 b of the fan unit 42 also acts as a pump to generatethe region of under pressure. There are fluid passageways 60 in a frontwall (i.e. the axial end proximal the fan) of the motor outer casing 30,and fluid passageways 61 in the wall of the diffuser 15. Thesepassageways fluidly couple the inside of the motor outer casing 30 tothe back side 42 b of the fan unit 42.

The back side 42 b of the fan unit 42 has a pressure gradient, with alowest pressure near the axis of rotation and a maximum pressure at theradially outermost extremity. The cooling air outlet from the motorcasing is formed by the internal fluid passageways 60, 61 which connectto the radially inner area. Preferably, they connect to the region ofgreatest under pressure (i.e. the lowest absolute pressure) at the backside 42 b.

The back side 42 b of the fan unit 42 may be a planar disc which isspaced from a front wall of the diffuser 15. The friction between theback side 42 b of the fan arrangement and the air trapped in the spacinggenerates a flow and pressure gradient, and thus functions as a pump.

While a planar back side 42 b of the fan unit 42 is sufficient, fanblades may be added to the back side so that the flow can be increased.Radial blades for example can also be used.

Thus, the fan is used to generate the region of under pressure for thesecondary flow using a back of the fan. The fan thus has front and backfunctional parts. The back functional part functions as compressor togenerate a pressure differential and this couples to the inside of themotor casing. The boundary 62 between the front and back sides 42 a, 42b of the fan unit provides some separation between the main suction flow(between the entrance flow 16 and the exit flow 18) and the secondaryflow (between the inlet flow 20 and the outlet flow 21) so that thesetwo flows do not (or only minimally) interact with each other.

However, the main flow and the secondary flow in this example combinedownstream of the motor outer casing to create a combined air outlet.The cooling air outlet from the motor casing is at the internalpassageways 60 and 61, whereas the eventually output air flow isdelivered from the main outlet 19.

The outlet flow 21 couples to the region of under pressure created bythe fan. There is a fluid coupling between this region of under pressureand the inside of the motor outer casing.

The direction of the secondary flow is for example constrained by thefan rotation. Thus, a region of under pressure is created adjacent thepassageways, and the flow direction means the air must be drawn from themotor outer casing (rather than being drawn from the radially outer partof the fan into the motor outer casing).

The fluid coupling has to be located in an area where the under pressurecreated by the fan can be localized and transferred. For this purpose, aresistance is present around the fan unit. The casing also acts as aresistance since otherwise the fan is exposed to the atmosphericpressure.

There may also be a pre-motor filter in front of the fan, which is apart of the dirt management system. This filter provides a resistanceand thus the areas surrounding the fan will have a negative pressurerelative to the atmospheric pressure.

For the example of FIG. 6 , if the upstream resistance i.e. in front ofthe fan is not present then the under pressure at the area where thecooling outlet is coupled might be lost. If the pressure at the regionto which the cooling outlet is coupled is at atmospheric pressure, thedifferential pressure is lost and the cooling flow will be lost. Thus,the flow resistance may pay a role in establishing the required pressuregradients in the system.

The pressure generated by the fan is dependent on the flow. However,even if the main suction flow is totally blocked, the secondary coolingflow will still be available to prevent overheating as it is generatedbased on a pressure differential separate from the main suction flow.Indeed, if the main suction flow is blocked, the motor runs without anyflow resistance, and this means the motor and fan perform at peakefficiency, thereby creating a highest negative pressure. A maximumvolume of cooling air will then be drawn in.

In this way, the system does not need conventional safety sensors foropening a safety valve when a main inlet is blocked. In conventionalsystems, the main suction flow is the cooling flow, so an interruptionto the main suction flow will result in overheating of the motor.

The back of the fan unit is also the most consistent area for generatingthe required under pressure, as it acts as an independent pump. The backof the fan unit does not need to be shaped as an impeller but can simplybe a solid disc. This solid disc will induce pressure variations whichare predictable and repeatable. Fan blades may however be added.

The pressure differences caused by the various flows are designed toavoid flow in the undesired directions. For example, since the outletflow 21 and the exit flow 18 combine, there is a physical (static)connection between the entrance flow 16 and the inlet flow 20 (sincethey both couple to the exit flow 18). However, the flow conditionsprevent the entrance flow 16 coupling back to the inlet flow 20 andthereby contaminating the secondary air flow.

FIG. 5 shows another cross section for the same design as FIG. 4 , withan additional outer casing 70 around the pump. The casing has a casinginlet (not shown) which is fluidly coupled to the cooling air inlets 22in chamber 70 a. It has a casing outlet which is isolated from thecooling air inlets 22 by the isolating ring 50 and couples to chamber 70b.

In the design of FIGS. 4 and 5 , it is possible that some drops ofmoisture from the moisture laden air that is transferred by the fan canend up or accumulate at the ends of the diffuser 15 where the flowleaves the fan and enters the diffuser blades. There is a chance thatwhen the appliance is in various orientations the water that isaccumulated on the diffuser 15 can ingress or creep into the gap betweenthe fan unit 42 and the diffuser 15 and then enter the motorcompartment.

In order to counter this situation the fan may be made as wide as orwider than the diffuser 15 so that moisture does not accumulate at theends of the diffuser. Also, a back part of the diffuser that faces themotor housing can have legs that can isolate the central part of the topcasing of the motor.

FIG. 6 shows a second example. It also shows some of the additionalparts around the pump.

The example of FIG. 6 also makes use of a region of under pressurecreated by the fan, but it couples to an inlet side of the fan, in themanner schematically shown in FIG. 2 . The fluid coupling for examplecouples to a region of maximum under pressure at the inlet side of thefan.

There is again an outer casing 70 with a casing inlet 71. The casingcouples to a post motor filter 72. The casing volume is fluidly coupledto the post motor filter 72 by an opening 74 in the casing. This opening74 lets moist air and circulated cooling air out to the filter 72.

The fan also has a pre motor filter 76 in front of the fan. Thisfunctions as a resistance element to create a desired pressure drop sothat the pressure at the main inlet is below atmospheric pressure. Thepre-motor filter is a part of the dirt management system.

The cooling air inlet 22 is again formed by the openings in the back ofthe motor casing. The cooling air outlet from the motor casing is formedby an internal passageway 80 which is connected to the region of underpressure. For example, a chamber 82 is formed which in this example iscoupled to the front of the fan, such that the region of under pressureis transferred to the chamber 82.

The chamber 82 is then used to draw the secondary air flow from themotor outer casing 30 via the internal passageway 80.

This example shows that the front of the fan may be used as the sourceof under pressure, and the secondary air flow does not need to pass theback of the fan.

FIG. 6 also shows pressure levels P1 to P6 along the cooling air flowpath. The pressure level P4 at the region of under pressure is below 1Atm (100 kPa) because of the filter 76, and after that the cooling flowis entrained with the main flow.

By way of example, P1=P6=1 Atm (100 kPa).

P4 is the region of maximum under pressure around the fan inlet, such as20 kPa below atmospheric pressure.

P3 is at an under pressure is marginally less than P4.

P2 is at an under pressure marginally less than P3.

P5 is at a maximum overpressure, such as 2 kPa above atmosphericpressure.

These are examples of the pressures in a normal working condition.

There is again a diffuser 15 but it has no major role in controlling thecooling flow.

The main flow enters as 16 and exits as 18 from the casing through theopening 74 and is not connected to the internal passageway 80 andchamber 82. The connection of the internal passageway 80 to an area ofunder pressure means it can draw air from the inlet 71 and then outthrough the chamber 82.

The internal structure of the pump arrangement ensures the cooling airdoes not short circuit to the outlet. This makes sure the drawn in airdoes pass through the motor casing and then to the outlet. A ring 84 forexample ensures there is a defined path through the pump arrangementwhich passes through the motor casing.

Thus, the underlying concept between these approaches is to use the fan,in particular an under pressure region created by the fan, to draw astream of cooling air as a secondary flow from the ambient surroundingsinto the motor casing.

In the first example, the back of the fan is used to create the underpressure. In this case, use is made of a set of holes 60, 61 in themotor outer casing and diffuser facing the back of the fan. Thesefunction as the cooling air outlet. The diffuser and the back side ofthe fan provide the required pressure gradients. Holes on the outer wallof the motor casing will act as the outlet.

In a second example, the front of the fan is used to create the underpressure. The front of the fan is connected to a cooling air outlet 80of the motor casing through a chamber 82 that also receives the underpressure. A filter or other structure provides the required pressuregradients.

The arrangement of FIGS. 4 and 5 above is based on a fluid coupling tothe back of the fan unit whereas FIG. 6 is based on a fluid coupling tothe front of the fan. Either approach may be used. However, when the aircooling outlet is coupled to the front of the fan it will havevariations in the under pressure level because this under pressure levelwill depend on the resistance that is connected in front of the fan(e.g. the fan) or around it (e.g. the fan casing design). This flowresistance is for example introduced by the dirt management system or bythe type (or state of blockage) of the vacuum nozzle. If the resistancechanges, the under pressure level will differ and thus the cooling flowthat is generated will also vary.

The use of the back of the fan as the pressure generating mechanism isthus more consistent.

The back of the fan also does not generate noise and as long as the fanis rotating with a suitable revolution speed, the generation of underpressure will be effective. Typically, the motor will rotate at a knownand consistent speed, so the back of the fan will generate a region ofconsistent under pressure.

In all examples, electronic components such as the main PCB andcontroller can be located upstream (in the sense of the flow of coolingair) of the motor, so that the inlet flow 20 passes and cools theelectronics before entering the cooling air inlet 22 and eventuallycooling the motor part 32. In this way, the cooling circuit not onlycools the motor but also cools the electronics. The air can be coldenough that it can still cool the motor after it has passed through theelectronics. The electronics can thus be cooled by the secondary airflowand isolated from the main flow as the moisture laden main flow canadversely affect the electronics by destroying or corroding them.

Similarly in all examples, electronic components such as the main PCBand controller can be located downstream (in the sense of the flow ofcooling air) of the motor, so that the inlet flow 20 enters the coolingair inlet 22 and cools the motor part 32 and thereafter eventuallypasses and cools the electronics.

The sequence of first cooling the electronics and then cooling the motoris generally preferred in case of a permanent magnet DC motor as thatavoids pollution of the electronics. To further elaborate, the air thatis exhausted from the permanent magnet DC motor may carry carbonparticles and hence is not suitable that it is then fed as air forcooling the electronics.

However, in case of a brushless DC motor, the sequence of first coolingthe motor and then the electronics or the other way around is consideredto be generally equally effective. This is because the air that isexhausted from a brushless DC motor is typically not contaminated bysuch particles due to the absence of carbon brushes in the motor, andthus is suitable for cooling the electronics even after passing themotor. Therefore, the cooling sequence can be adapted, in whichever wayas mentioned above depending on the type of motor, to not only to coolthe motor but also the electronics.

FIG. 7 shows a wet vacuum cleaner 100, comprising a vacuum cleaner head112, and a pump (motor 114 and fan 116) for delivering suction to thevacuum cleaner head. The vacuum cleaner head connects to a dirty airinlet of the main body of the vacuum cleaner.

A cyclone unit 118 is provided for separating liquid and particles froma flow generated by the suction of the motor and fan.

The motor comprises the bypass motor as described above, with asecondary flow of air for cooling. This type of motor can tolerate watercontent in the air flow, because the drawn in air flow is not used formotor cooling and is isolated from the motor parts. Instead, ambient airis drawn in to the motor for cooling purposes as described above.

The cyclone unit 118 is part of a wet dirt management system upstream ofthe pump. It has a collection chamber 128 for collecting the separatedmoisture and dirt (i.e. a waste water collection reservoir). A filtersection 120 is provided between the outlet flow of the cyclone and themotor and fan, and an outlet filter section 121 is provided downstreamof the pump for filtering the combined main flow and secondary flowbefore it is expelled to the ambient surroundings.

FIG. 7 also schematically shows control electronics 122, wherein thecontrol electronics is cooled by the secondary flow of air, before thesecondary flow of air enters the motor outer casing.

The cyclone has a cyclone axis of rotation 124. This axis may beparallel to the inlet flow direction (as shown) or it may beperpendicular, depending on the configuration. The collection chamber128 is for example below the cyclone chamber (when the vacuum cleaner isupright) so that water is collected under gravity. There is a handle 130at the opposite end to the head 112.

The vacuum cleaner shown is a stick vacuum cleaner. Of course, it may bean upright vacuum cleaner or a drum vacuum cleaner. The inventionrelates to design features of the motor and fan, and may be applied toany wet vacuum cleaner.

The user may be required to deliver water to the surface being vacuumedindependently of the vacuum cleaner. However, the wet dirt managementsystem may instead also include a clean water reservoir for deliveringwater to the vacuum nozzle. The vacuum cleaner head for example has arotary brush to which water is delivered from the clean water reservoir.

Variations to the disclosed embodiments can be understood and effectedby those skilled in the art in practicing the claimed invention, from astudy of the drawings, the disclosure and the appended claims. In theclaims, the word “comprising” does not exclude other elements or steps,and the indefinite article “a” or “an” does not exclude a plurality.

The mere fact that certain measures are recited in mutually differentdependent claims does not indicate that a combination of these measurescannot be used to advantage.

If the term “adapted to” is used in the claims or description, it isnoted the term “adapted to” is intended to be equivalent to the term“configured to”.

Any reference signs in the claims should not be construed as limitingthe scope.

1. A pump for use in a vacuum cleaner to generate a suction forapplication to a vacuum cleaner dirty air inlet, comprising: a motorouter casing; a motor part in the motor outer casing; a fan outside themotor outer casing, driven by the motor part, having a main inlet and amain outlet, wherein the fan generates a main suction flow between themain inlet and the main outlet and creates a region of under pressure; acooling air inlet to the motor outer casing; a cooling air outlet fromthe motor outer casing; and a fluid coupling between the cooling airoutlet and the region of under pressure such that a secondary flow ofair is sucked through the cooling air inlet resulting in a cooling ofthe motor, wherein the cooling air inlet and the main suction flow areseparated from each other.
 2. The pump as claimed in claim 1, whereinthe fan is located inside a fan casing and wherein the region of underpressure created by the fan is located at least partially inside the fancasing and outside the motor outer casing.
 3. The pump as claimed inclaim 1, wherein the region of under pressure created by the fan couplesto an inlet side of the fan.
 4. The pump as claimed in claim 3, whereinthe fluid coupling couples to a region of maximum under pressure at theinlet side of the fan.
 5. The pump as claimed in claim 1, wherein theregion of under pressure created by the fan is located adjacent themotor outer casing couples to the inside of the motor outer casing. 6.The pump as claimed in claim 5, wherein the fan has a front side outsidethe motor outer casing and a back side which faces and couples to theinside of the motor outer casing, and wherein the back side acts as apump to generate said region of under pressure.
 7. The pump as claimedin claim 6, wherein the fluid coupling couples to a region of maximumunder pressure within the front side of the fan or the back side of thefan.
 8. The pump as claimed in claim 1, wherein the main outlet isdirected around the outside of the motor outer casing.
 9. The pump asclaimed in claim 1, wherein the motor part comprising: a brushless dcmotor; or a permanent magnet dc motor.
 10. A pump and filter unit,comprising: the pump as claimed in claim 1; and a filter sectiondownstream of the pump.
 11. A vacuum cleaner, comprising: a main bodyincluding the pump as claimed in claim 1; a vacuum cleaner dirty airinlet coupled to the main body to receive a suction generated by thepump; and a dirt separation unit upstream of the pump.
 12. The vacuumcleaner as claimed in claim 11, further comprising a filter sectionthrough which a flow generated by the pump is passed, wherein the filtersection is downstream of the pump.
 13. The vacuum cleaner as claimed inclaim 11, further comprising control electronics, wherein the controlelectronics is cooled by the secondary flow of air.
 14. The vacuumcleaner as claimed in claim 11, further comprising control electronics,wherein the control electronics is cooled by the secondary flow of air,before the secondary flow of air enters the motor outer casing.
 15. Amethod of cooling a motor of a vacuum cleaner pump which is for drivinga fan to generate a main suction flow and a region of under pressure,the main suction flow being for application to a vacuum cleaner dirtyair inlet, and the motor being contained within a motor outer casing,the method comprising: providing a fluid coupling between a cooling airoutlet of the motor outer casing and the region of under pressure, suchthat a secondary flow of air is sucked through the cooling air inletresulting in a cooling of the motor, wherein the cooling air inlet andthe main suction flow are separated from each other.
 16. The pump asclaimed in claim 1, wherein the fan further comprises a pre motor filterto create a pressure drop so that pressure at the main inlet is belowatmospheric pressure.